Three in-the-moment improvisations explore Jörg the variegated textures available from strings and percussion, aided and abetted by electronics. Connective tissue between the two discs is British table-top guitarist Keith Rowe, former and perhaps future member of AMM, who has been involved in this sot of non-idiomatic improvisation for almost four decades.

Each disc features him in a different, virtually hypnotic sound situation. Squire is a nearly 43-minute almost constant basso ostinato-shaped meeting between Rowe and one of his younger acolytes, Australian guitarist Oren Ambarchi. Although sonically similar, additional timbres on Tensions add another layer of interpretation to the electro-acoustic mixture.

Recorded live in Berlin, the double Nexsound CD celebrates the fifth anniversary of Perlonex, a German trio made up of Jörg Maria Zeger on guitars, percussionist Burkhard Beins and Ignaz Schick on turntables, objects and live electronics. The sound of the first of the two CDs, which adds Rowe to the existing trio, is notable as slightly inflated version of the table-top guitarists ongoing saga. Comparable, but appending distinctive patterns to the mix, is the second CD of the set, which links Perlonex with American composer/performer Charlemagne Palestine on piano and organ-like keyboards.

Symbolist where Rowes contribution is unadorned and ritualistic in his output, where the guitarists improvising is plainly agnostic, Palestine has links to 19th century Impressionism and 20th century Minimalism. His single contributions is no less mesmerizing than Rowes on the other two sessions, yet only with his piano chording are you confident enough to ascribe textures to a single acoustic instrument.

Palestines repetitive arpeggios and other vibrational overtones would seem antithetical to the stripped down, intermittent playing of Schick and Beins, for instance, who are often found in the company of other reductionists, such as trumpeter Axel Dörner and inside pianist Andrea Neumann. However when his swirling organ washes and tremolo hammered key strokes reach a unambiguous mass of counter tones, these tones append unequalled chromatic progressions to Perlonexs conception. Then the trio responds in kind.

Soon Palestines playful piano clusters, lying on top of organ-like, repetitive tones are layered in an aural sandwich with melodic guitar riffs, repeated hammering, as if a blunt object was striking an unlatched cymbal, and no-input turntable crackles and crunches. Concentrated, the polyphony turns to a repetitive ostinato which itself ascends to a crescendo of near-vocalized envelopes of ringing counter tones and metronomic sound cadences. Evolving further in broken octaves, piano key clipping and pinging, plus percussion rumbles, chain rattles and maracas shakes continue to vibrate among the undulating organ chords.

In contrast, Perlonex plus Rowe appears as four interlocking parts of a single motor-driven block. Humming electronic pulsations characterize the four-man output with only slivers of crumbling percussion pressure and guitar fuzz tone intermittently audible.

Soon the overwhelming wave form flutters become more diffuse, more drone-like and more circular  all tension and no release. With the recurring single tone triggering an envelope of grinding pulses, the cumulative sound picture moves from forte to fortissimo  almost quadruple the volume at which the suite began.

A penultimate variation interrupts interlude of sequences scrapes with two drones  one inchoate and shrill, and the other low-pitched and buzzing. As the grinding timbres snake from one side of the interface to the other, the concentrated intensity is almost visual. Traditionally rondo-like in theory, yet pitch-modulated microtonal in execution, the piece finally shudders towards a finale, which never arrives. Instead the sound diminishes, first into wisps of the initial repeated theme, and then it dissolves into silence.

Divide that interface in half, and the parameters of the dual-guitar face off on Squire come into focus. Dense, mesmerizing quivers take up most of the aural space here as Rowe and Ambarchi appear fixated on similar scraped pulsations and blurry, ring-modulator-like signaling. Early on, the suggestion of distant voice emerging from a manipulated radio set  a Rowe trademark  is more sensed than heard. Yet, as the spluttering signals descend, they seem to spread out and coat larger portions of the aural space. With the next section foreshadowing a slightly quicker tempo rather than the glacier-paced commencement, a crescendo is promised. But instead, the undulating drone suddenly ceases, as systematic motor sounds and scraped string thumps and flanging pitch changes substitute for it.

Avoiding Musique Concrète by a hair  or perhaps more appropriately a quiver  these overlaid staccato drones and nasal whirring separates into inchoate but layered passages that are abrasively sharp and almost ear-wrenching. As a finale, not unlike the Rowe-plus-Perlonex interchange, these triggered buzzes and high-pitched whistles almost fade away to be replaced with barely-there oscillations that almost replicate the tracks beginning. The conclusion itself is anti-climatic. As the bursts of improvised intonation diminish, you realize the piece is finished because sound has ceased. This is a long-standing AMM trope which only works in certain circumstances.

If youre familiar with the work of any, or all of these minimalist improvisers, than the slender differences between the creations of Rowe and Ambarchi may fascinate you, as will the guitarists sonic interjections into Perlonex group sound. Those less committed will likely be more drawn to the subversive melodiousness of the trios meeting with Palestine.